From f179a2fc2e23ff623344717eec3b8a443a57222a Mon Sep 17 00:00:00 2001 From: Ramalingam C Date: Sat, 3 Feb 2018 03:39:04 +0530 Subject: [PATCH] drm/i915: Stop encryption for repeater with no sink If a HDCP repeater is detected with zero downstream devices, HDCP spec approves either of below actions: 1. Dont continue on second stage authentication. Disable encryption. 2. Continue with second stage authentication excluding the KSV list and on success, continue encryption. Since disable encryption is agreed, repeater is not expected to have its own display. So there is no consumption of the display content in such setup. Hence, incase of repeater with zero device count, this patch fails the HDCP authentication and stops the HDCP encryption. v2: Rephrased commit msg and added comments in code [Seanpaul] v3: No changes. Added Reviewed-by tag. Signed-off-by: Ramalingam C Reviewed-by: Sean Paul Signed-off-by: Sean Paul Link: https://patchwork.freedesktop.org/patch/msgid/1517609350-10698-3-git-send-email-ramalingam.c@intel.com --- drivers/gpu/drm/i915/intel_hdcp.c | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-) diff --git a/drivers/gpu/drm/i915/intel_hdcp.c b/drivers/gpu/drm/i915/intel_hdcp.c index de9a925..0a1ef82 100644 --- a/drivers/gpu/drm/i915/intel_hdcp.c +++ b/drivers/gpu/drm/i915/intel_hdcp.c @@ -166,10 +166,16 @@ int intel_hdcp_auth_downstream(struct intel_digital_port *intel_dig_port, return -EPERM; } - /* If there are no downstream devices, we're all done. */ + /* + * When repeater reports 0 device count, HDCP1.4 spec allows disabling + * the HDCP encryption. That implies that repeater can't have its own + * display. As there is no consumption of encrypted content in the + * repeater with 0 downstream devices, we are failing the + * authentication. + */ num_downstream = DRM_HDCP_NUM_DOWNSTREAM(bstatus[0]); if (num_downstream == 0) - return 0; + return -EINVAL; ksv_fifo = kzalloc(num_downstream * DRM_HDCP_KSV_LEN, GFP_KERNEL); if (!ksv_fifo) -- 2.7.4